It has been known that cathode coils made of tungsten wire are used in X-ray tubes. Such tungsten coils are held on metal straps or metal leads, which consist of, e.g., molybdenum. Heating coils are fastened to the leads generally by welding, e.g., argon arc welding or microplasma welding. The cathode coils may be damaged in the area of fastening during such welding processes.